The Ligue 1 champions drew their opening two matches, before edging past newly-promoted Nantes 2-1 on Sunday.
While he admits that Les Canaris played well, Blanc feels that his side need to work harder ahead of their next match.
"Everyone expected this victory," Blanc said. "It was difficult because Nantes played a beautiful game.
"Certain situations should have been better managed, we have not done that, we have suffered up to the last second. I knew before the game that the rapport may not be perfect.
"We are behind many teams in terms of preparation. We have very high level attackers that many teams envy, there is a balance to be struck."
PSG host Guingamp this weekend.